Alkylnitrenes

Intramolecular alkylnitrene addition to an alkenic moiety situated S,e to the electron deficient center has been utilized for the preparation of bi- and tri-cyclic aziridines (Scheme 11) (68JA1650). Oxidation of the primary alkylamine can be effected cleanly with NCS, LTA or mercury(II) oxide. 

The intramolecular chemistry of alkylnitrenes resembles that of alkylcarbenes in general. 

In fact, rearrangements of singlet alkylnitrenes generated in frozen matrices cannot even be suppressed by developing strain in imine products such as 1-3, although some triplet nitrene is detected by EPR and UV-vis spectroscopy upon low-temperature photolysis of 1-azidonorbornane. ... 

Photolysis of 25 in ether-isopentane-ethanol (EPA) at 77 K produced a species that absorbs at 336 nm. The carrier of this spectrum is persistent for at least 1 h at 77 K, but disappears upon annealing. Based on the EPR spectrum and the similarity of the UV spectrum to those of triplet alkylnitrenes, the species absorbing at 336 nm was attributed to the triplet phosphorylnitrene. ... 

G. Nitrenes.—The importance of nitrenes is well known,128 and the prototype NH has been extensively studied in the past,129 but until recently no ab initio work has appeared on other nitrenes. The simplest alkylnitrene, MeN, has not been studied spectroscopically but three recent papers have investigated the ground state and some excited states.11 130 131... 

For the homologous alkylnitrenes no electronic spectra have been reported so far. 

If arylsulphonylnitrenes are generated in aliphatic hydrocarbons, better yields of hydrogen abstraction products as in the case of alkylnitrenes are obtained. Thermolysis of p-toluenesulphonylazide in cyclohexane 25> gave 5% yield of p-toluenesulphonylamide, whereas 40% yield was reported also 58>. Thermal decomposition of o-substituted phenylazides 20, 21, 22 in dodecane via abstraction afforded amides 23, 24, 25. 

Alkylnitrenes are very poor in functionalizing C—H bonds, even if the insertion is intramolecular. Earlier claims that pyrrolidines (6) could be formed by insertion of alkylnitrenes derived from simple alkyl azides have subsequently been disproved,and the only apparently genuine example of a reaction of this type involves the azidosteroid 6P-azido-5a-pregnane (7), which leads to functionalization of the... 

The formation of small amounts of the hydrogen abstracdon products, amines (128) and (130) from the thermolysis in the absence of solvent of azides (127) and (129) also lends some support to the dew that a free alkylnitrene is formed . However, routes to the amines other than hydrogen abstracdon may be envisaged. For example, 1,3-dipolar addidons (of the type described for azide 119) to olefins and imines formed in the thermolysis of the azide, followed decomposition of the adducts and hydrolysis could give 128 and 130. 

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